1. Field of the Invention
This invention relates to a system for distributing and selecting audio or video information on a network and the method implemented by this system.
2. Description of Related Art
British patent 2166328 discloses a device which distributes audio or video information over a coaxial cable network requiring a specific bus of the ISDN type comprising a telephone network and a communications bus for the other devices, with the communications bus containing remote control boxes, each linked to an adapter device connected to the bus.
A network such as this has the drawback that it requires wiring of several networks, first coaxial type wiring, second wiring for the ISDN-type telephone network, and finally third wiring for the communications control bus.
Another patent application, European patent no. 140493, circumvents these drawbacks by using only the coaxial network to distribute audio information originating from a jukebox unit, using on the cable network at least one channel allocated to transmission of audio information. This channel is divided into subchannels and each audio selection is frequency-multiplexed. Thus 75 to 200 audio channels are sent over a video channel with a bandwidth of 6 MHz. A conversion box makes it possible to select each of the subchannels and thus for the user to hear the song carried by this subchannel. The drawback of a system such as this is that the user cannot determine the beginning and the end of the song, since all the selections are played without interruption, and the waiting time can be up to 30 seconds. Another drawback of this system design is that it is not possible to simultaneously transmit video and audio information. In fact, in order to transmit video information the primary carrier of each channel must be taken, and in this case, per channel it will no longer be possible to transmit more than one video information item associated with one or two audio information items of acceptable quality, among which one of these two audio information items corresponds to the one associated with the video information. Thus, in order to transmit video information corresponding to 200 selections, the saturation point would soon be reached and all available channels would be occupied. In this case, transmission of television channels would no longer be possible and in any case the number of audio information items will be less than 10.